1. Field of the Invention
The present invention relates to a road surface member used in a tire testing machine for performing a performance test of a tire, and a manufacturing method of the same.
2. Description of the Related Art
In a production line of a tire, various performance tests are performed by a tire testing machine in which a rotary drum or a flat plate is pushed onto a rotating tire.
Japanese Unexamined Patent Application Publication No. H4-350536 discloses a tire testing machine in which a road surface is coated with a thermally-sprayed film made of metal carbide such as tungsten carbide, chromium carbide, and titanium carbide so that the road surface of a rotary drum or a flat plate made of iron or aluminum, the road surface serving as a contact surface with a tire has a friction characteristic close to asphalt.
However, with the thermally-sprayed metal carbide film, uniformity of thickness of the thermally-sprayed film and uniformity of surface roughness are not easily controlled, and hence roundness of the rotary drum or flatness of the flat plate is not easily increased.
Concave and convex parts having arithmetic mean roughness of about Ra 16 are created on the road surface to which the thermally-sprayed metal carbide film is thermally sprayed. Therefore, a road surface state is inferior, so that the roundness of the rotary drum or the flatness of the flat plate cannot be precisely measured. In addition, since tremor of the rotary drum and rolling of the road surface are added in a meter provided in a tire shaft, there is sometimes a case where a right value cannot be measured. In particular, in a running test with rotation speed of the tire of not less than 60 km/h from normal speed to high speed region, an influence of the road surface state over a test result is increased.
Thus, it is thought that the road surface is processed. However, since the thermally-sprayed metal carbide film has high hardness, a diamond grindstone is used. Furthermore, since the rotary drum and the flat plate of the tire testing machine are large by themselves, processing is not easily performed and cost is high. Therefore, in an actual situation, the rotary drum and the flat plate of the tire testing machine are used in a state that the thermally-sprayed metal carbide film is thermally sprayed.
In a case where a plurality of tire testing machines is used, a state of the thermally-sprayed metal carbide film is differentiated for each of the tire testing machines, and there is a large individual difference in the roundness and the flatness. Thus, even with tires having the same lot, the test result is varied, and characteristics of the tires cannot be simply compared.
Further, the road surface to which the thermally-sprayed metal carbide film is thermally sprayed is rough and has large concave and convex parts as described above. Thus, depending on test contents such as a high speed test and a control and drive test, there is sometimes a case where rubber of the tire is accumulated in the concave parts, so that a friction coefficient is changed or the roundness is further largely deteriorated. Removal of the rubber accumulated in the concave parts is considerably troublesome.